Suncourt Flush Fit Register Air Booster Fan with Adapter Plate - HC500-W - White MAXIMIZE AIRFLOW - Enhance the performance of your existing furnace or air conditioner by boosting airflow up to 85%. Enhance your airflow--and comfort! SAVE MONEY: Maximize the heating or air conditioning from your forced-air system with a minimum increase in energy use. Unit continues to run after your forced-air shuts off, pulling every bit of heat or cold air into your home. QUIET OPERATION: Quiet, 3-speed dual fans increase airflow without excess noise. EASY INSTALLATION: This unit drops directly into a standard 4" x 10" register without any modification. Includes adapter for wall installation. SET AND FORGET: Unit automatically switches on when airflow is sensed. All you have to do is set the fan speed and desired temperature.